A Small Hot Tub for a Small Backyard: Sizes, Layouts and How to Build One

Last updated: September 2026

Have you ever dreamed of having a hot tub in your garden or backyard, but thought it was impossible because you don’t have much space? Think again. A small hot tub gives you all the warm water and bubbles, even in a tiny garden or on a patio. And when you build it yourself, it fits the space you’ve actually got, not one of a handful of standard shell sizes.

In this guide I’ll cover how big (or small) a small hot tub should be, how to lay one out so it doesn’t feel cramped, what to build it from, and how to heat and plumb it. A small tub has some real advantages, starting with the heating bill.

How big is a small hot tub?

That might sound like an odd question, but it isn’t. The right size depends on how many people will use it and how much space you have. A small hot tub is generally one that seats two to four people comfortably.

For a built tub, I’d say a small hot tub is 6ft x 6ft internally at most, perhaps 7ft x 7ft at a push. Much smaller than 6ft x 6ft and it gets hard to fit proper seats, a footwell and the jets without everyone’s knees meeting in the middle.

Internal size	Metric	Typical seats	Floor area vs 8ft x 8ft
6ft x 6ft	1.83m x 1.83m	2–3	About 44% less
7ft x 6ft	2.13m x 1.83m	3–4	About 34% less
7ft x 7ft	2.13m x 2.13m	4	About 23% less
8ft x 8ft (for comparison)	2.44m x 2.44m	4–6	The most popular DIY size

Seat counts depend on your layout and how friendly you are with each other, so treat them as a guide. When you choose the size, think about how many people will usually be in it, not the one party a year.

Leave room around it

The tub’s internal size isn’t the space it takes up. You also need to allow for:

• The walls and coping. Block or ICF walls plus coping add roughly 30–40cm (12–16in) on each side, so a 6ft x 6ft tub is nearer 8ft x 8ft on the outside.
• A safe way in. Steps inside take up seating, and steps outside take up garden. See Hot tub steps: the ultimate guide.
• Somewhere for the cover to go when you’re in it.
• The control room, plus room to get in and service it.
• Your electrics. The isolator needs to be within sight of the tub but out of reach from it. In the UK that’s typically at least 2m away.

Layout tricks for a small space

• Use the corner. Tucking the tub into a corner of the garden uses two existing boundaries and gives you privacy for free. Check that you can still get round the back to the plumbing, though.
• Mix the seat heights. One lower seat and one higher one make a small tub feel bigger and suit people of different heights.
• Consider a corner lounger if it’s mainly for two. A lounger takes a lot of space, so think carefully in anything under 7ft.
• Raise it partly out of the ground. A semi-sunken tub makes a handy seat-height edge to sit on, and the raised part can hide steps. See In-ground hot tub designs.
• Put the control room under a deck or against a boundary wall, but keep it close to the tub and ideally below the water line. See Hot tub control room position.
• Keep the shape simple. Squares and rectangles give you the most seating for the space and are the easiest to build and cover.

For more on screening a small garden, see Hot tub privacy ideas, and for seat heights and depths, What makes a good DIY hot tub design?

What should I build a small hot tub from?

Building a hot tub from ICF (insulated concrete form) blocks is a great option if you want something durable, long-lasting and energy-efficient that fits your space exactly. ICF blocks are two layers of rigid foam insulation held together by webs. You stack them, fill them with concrete, and end up with a strong reinforced concrete wall with the insulation already on both sides. That insulation matters even more on a small tub, which has a lot of wall for the amount of water it holds.

Here’s how an ICF build goes, in the right order:

1. Decide the size and shape, and get a plan with the seat heights and plumbing routes.
2. Dig and lay a compacted sub-base.
3. Fit the main drains and a hydrostatic relief valve, then pour a reinforced concrete slab with starter bars sticking up where the walls go. The ICF sits on this slab, not on loose gravel.
4. Stack the ICF blocks on the slab, level and square, cutting them to size with a saw. Add vertical rebar.
5. Set the plumbing through the walls: jets, returns, skimmer and light conduits all go in before the concrete.
6. Pour the concrete into the ICF and let it cure.
7. Render, apply a pool-rated waterproofing membrane and flood test it.
8. Tile it, fit the coping, and finish the control room.

There’s more in ICF block hot tub, The best ICF blocks for building a hot tub and TubBlox. Block and poured concrete work well too. See DIY hot tub construction: block, ICF or poured concrete?

If you want small and cheap rather than small and permanent, a stock tank hot tub is worth a look. A 6ft round tank fits almost anywhere.

Heating a small hot tub

This is where a small tub really pays off. Less water means less to heat, and the heat-up time drops with it.

As a rule of thumb, every 1kW of heat adds roughly 0.86°C per hour to 1,000 litres of water (about 1.5°F per hour to 265 US gallons), before heat losses. So a typical 3kW spa pack element on, say, 1,500 litres manages around 1.7°C an hour, while on a bigger 2,800-litre tub like mine it’s under 1°C an hour. The full maths is in Hot tub heaters explained.

• Electric (in the spa pack): easy to install and built into the spa pack. It’s slow on a big DIY tub, but on a small one it’s more workable. It’s still the most expensive way to run.
• Gas or propane: the fastest, whatever the weather, but it costs more to install, needs a qualified gas installer and a constant fuel supply. Good if you like to decide an hour beforehand that you fancy a soak.
• Air source heat pump: the cheapest to run. The US Department of Energy puts pool heat pumps at a COP of 3 to 7, meaning 3 to 7 units of heat for every unit of electricity. They cost more to buy and lose efficiency in cold weather, but when I fitted one to my own tub, I cut my running costs by 66%.

A small tub may tempt you towards a small plug-in heat pump. Be careful: some only run in mild weather or deliver less heat than a 3kW element when it’s cold. See my reviews of the Onda Mini and the Balboa Clim8zone II Mini, and How to choose the right air source heat pump.

Whatever you choose, a well-fitting insulated cover and insulation around the shell save more than any heater upgrade. See DIY hot tub insulation.

Plumbing a small hot tub

You need to plan where the jets and any water features go, because placement affects both the water flow and how comfortable the seats are. In a small tub it’s easy to fire jets straight across at someone else’s back, so think about who sits where.

• Jets: a small tub rarely needs more than one jet pump. One pump runs up to about 16 jets. See DIY hot tub jets and How many pumps do you need?
• Filtration: a skimmer to take debris off the surface, and twin main drains with anti-entrapment covers, so no single drain can trap anyone. The filter and pump keep the water clean and clear. See How to install a skimmer.
• Water features need their own pump. Don’t tee them off the jets.
• Pipe: pressure-rated PVC pipe and fittings, solvent-welded properly. See Hot tub pipe and How to make a PVC solvent weld joint.
• Insulate the pipe runs to the control room to cut heat loss.

Plumbing is crucial whatever the size of the tub, and it’s where most leaks come from. Take your time, pressure test before anything is buried, and it’ll last for years. This is certainly an area I can help with. The basics are in DIY hot tub plumbing.

Common mistakes with small hot tubs

• Going too small. Under about 6ft x 6ft, seats and legs start to clash.
• Forgetting the outside dimensions. Walls, coping, steps and the control room all need space.
• Too many jets for one pump, or jets pointing at the seat opposite.
• No insulation, because “it’s only small”.
• Nowhere to put the cover.
• Squeezing the control room in where you can’t get to the filter. I made mine too small and had to rebuild it.

Planning a small hot tub?

I have ready-made plans in small sizes: 6ft x 6ft, 7ft x 6ft, 7ft x 7ft and, in metric, 2.13m x 2.13m. They give you the dimensions, the plumbing layout and a shopping list, so you know it’ll fit before you start. The full range is on the hot tub plans page.

If your space is an awkward shape, design your own layout in the free Tub & Pool Designer Pro software, and I can turn it into architectural CAD and a 3D plumbing design. There are more ideas for small spaces in Mini pool ideas, and on my YouTube channel.

FAQs

What is the smallest practical size for a DIY hot tub?

Around 6ft x 6ft (1.8m x 1.8m) internally. Below that it’s hard to fit proper seats, a footwell and jets without people’s legs clashing.

How much space do I need for a small hot tub?

Add roughly 30–40cm (12–16in) on each side for walls and coping, plus room for steps, the cover and the control room. A 6ft x 6ft tub is nearer 8ft x 8ft on the outside.

Is a small hot tub cheaper to run?

Yes. Less water means less to heat and a faster heat-up. Insulation, a good cover and an air source heat pump make the biggest difference to running costs.

Can I use the spa pack heater on a small hot tub?

Yes. A 3kW element copes far better with a small tub than a big one, although it’s the most expensive way to run. Many people add a heat pump later.

How many people fit in a 6ft x 6ft hot tub?

Two to three comfortably, depending on the seat layout.

Got a small space you’re trying to squeeze a tub into? Tell me about it in the comments below. I read them all.

Cheers,
Andi

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Thanks - Andi

 

Hi, Andi here. I own Buildahottub.com and also write all of the articles and info pages on the site. Some years back now, I built my own hot tub but struggled to find the information I needed. So, once my tub was complete, I started this website to help others in their own pursuit of hot tub and plunge pools DIY building information.

Fast forward to 2025, I've helped over 1400+ DIY customers just like you all over the world build hot tubs and pools. Have a good look around the site, there are lots of resources here. Please do get in touch if I can help you. - Cheers, Andi